window.onload = function(){
    var info = document.getElementById("info");
    var checkbox = document.getElementsByTagName("input")[0];
    var button = document.getElementsByTagName("button")[0];

    info.onscroll = function(){
        //console.log("1");
        //console.log(this.scrollHeight);
        if(this.scrollHeight-this.scrollTop==this.clientHeight){
            //console.log("1");
            checkbox.disabled=false;
            button.disabled=false;
        }
    }
};